Hydrothermal process for the treatment of lead glass with recovery of lead metal, soluble and insoluble silicates and silica

Active Publication Date: 2017-09-28
HELLATRON SPA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The patent is for a method to extract lead from insoluble silicates, which are obtained after treating glass with a alkaline substance. The method uses electrolysis to recover lead from the treatment process. The method reduces electrolysis time by controlling the concentration of lead in solution and avoids low current yields. The method also includes a method to reduce residual lead in solution by adding controlled amounts of metallic zinc. The technical effects of this patent are increased efficiency and efficiency of extracting lead from insoluble silicates.

Problems solved by technology

The treatments that are performed on older television sets are limited to the recovery of plastic materials, electronic boards, electric cables, coils and other metal materials, while operations on the glass parts, consisting of a glass screen, with a high content of barium and strontium, and a glass funnel with high lead content, are limited.
As described in EP 2455500 A1, the process is effective in recovering from a separate solid phase the lead in the form of sulphide present in the soluble phase, but the process requires the use of Na2S or H2S, which are very toxic substances that require special care while using them.
In EP 2455500 A1, however, there is neither mention of the lead present in the insoluble silicates nor of methodologies for its recovery, so that recovery of this material is not complete, and the process also creates a solid material containing lead without indicating any destination thereof.

Method used

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  • Hydrothermal process for the treatment of lead glass with recovery of lead metal, soluble and insoluble silicates and silica
  • Hydrothermal process for the treatment of lead glass with recovery of lead metal, soluble and insoluble silicates and silica

Examples

Experimental program
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example 1

[0026]The following masses are loaded in an autoclave: 600 kg of lead glass ground with a particle size less than 1 mm, 180 kg of 99.9% pure solid sodium hydroxide and 420 kg of water. The lead glass being used had a PbO content of 18.31% by weight, determined by X-ray diffraction, equal to 17% of Pb expressed as metal. The mass was heated to 205° C. and stirred for two hours. The registered autogenous pressure was 16 bar. At the end of the reaction, the mass was cooled and diluted with 900 liters of water. 102 kg of lead, expressed as metal, was found in the resulting suspension.

[0027]The suspension was transferred into a mixer and maintained under constant stirring at a temperature of 55-60° C. The suspension was continuously sent to a filter so as to separate the solid phase, constituted by insoluble silicates, fromt part of the liquid phase, consisting of sodium and potassium soluble silicates. The separated solid phase was recycled into the mixer while the separated liquid phas...

example 2

[0031]The procedure of Example 1 has been repeated, with the differences that the mass is cooled down and diluted with 600 liters of water at the end of the alkaline etching reaction on the ground glass. By operating as described in Example 1, 1200 kg of soluble silicate with a concentration of 37% by weight, a density of 1.38 g / ml and a value of R=1.7 were eventually obtained. The recovery of metallic lead and insoluble silicates were the same as those indicated in Example 1.

example 3

[0032]The procedure of Example 1 has been repeated, with the differences that the time of the alkaline etching reaction on the glass was reduced to 1 hour and 30 minutes, but the temperature was elevated to 215-218° C. The reaction mass was diluted with 400 kg of water, obtaining eventually 1000 kg of soluble silicate with a concentration of 41.9% by weight, density of 1.43 g / ml, and R=1.8 (by moles). The recovery of metallic lead was higher than 99.84%. Furthermore, the electrolysis reaction was carried out with a current density of 700 A / m2, with a 15% reduction of the time for the electrolytic recovery of lead without significant changes on current efficiency.

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Abstract

There is described a process completely performed in aqueous phase, which provides a heat etching of lead glass with aqueous solutions of strong alkali followed by an electrolytic treatment of the suspension so obtained, in order to recover metallic lead and obtain soluble silicates, separated from insoluble silicates, both lead-free. The process also provides for the production of pure silica, derived from the soluble silicates, and a possible use thereof to increase the ratio between silica and sodium oxide, which characterizes the specifications of the soluble silicates. The electrolysis for the recovery of metallic lead is implemented in a cell in which the polarity of the electrodes is periodically reversed, to obtain the detachment of the metallic lead deposited on the cathodes.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a process for the recovery of lead contained in the rear portion (funnel) of the traditional cathode ray tube screens (CRT).STATE OF THE ART[0002]EU regulation for Electrical—Electronic Waste (WEEE) have been transposed in Italy by Legislative Decree 151 of 25 Nov. 2005 and the collection of old CRT television sets, classified as R3, implemented by specialised consortia and companies, has resulted in a recovery of over 75,000 tons in 2012.[0003]The treatments that are performed on older television sets are limited to the recovery of plastic materials, electronic boards, electric cables, coils and other metal materials, while operations on the glass parts, consisting of a glass screen, with a high content of barium and strontium, and a glass funnel with high lead content, are limited. The minimum content of this metal in the glass funnel amounts to 17%.[0004]The two types of glass are separated using different methods and t...

Claims

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Application Information

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IPC IPC(8): C22B3/00
CPCC22B13/045C03C1/024Y02P10/20
Inventor MODICA, GIOVANNI
Owner HELLATRON SPA
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